Internal combustion engines generate exhaust as a by-product of fuel combustion within the engines. Engine exhaust contains, among other things, unburnt fuel, particulate matter such as soot, and harmful gases such as carbon monoxide or nitrous oxide. To comply with regulatory emissions control requirements, engine exhaust must be cleaned before it is discharged into the atmosphere.
Engines typically include after-treatment devices that remove or reduce harmful gases and particulate matter in the exhaust. For example, a diesel engine can be equipped with a diesel oxidation catalyst (DOC) that promotes oxidation of unburnt fuel, carbon monoxide and/or nitrous oxide, and a diesel particulate filter (DPF) that traps particulate matter. Over time, the increasing volume of trapped soot impedes the flow of exhaust through the DPF and degrades engine performance. One commonly used technique for in-situ cleaning or regeneration of the DPF involves raising the temperature of the DPF above a combustion or oxidation threshold of the soot particles accumulated on the DPF. In most cases, this is achieved by heating the exhaust before it enters the DPF. One technique of heating the exhaust consists of injecting fuel into the exhaust and oxidizing it in the presence of a DOC located upstream from the DPF. Heat generated from the oxidation reaction heats the exhaust as it flows through the DOC before entering the DPF. When the soot particles in the DPF come into contact with hot exhaust, they oxidize.
To ensure that heated exhaust can flow through a DOC into a DPF, one end of the DPF may be fixedly attached to the DOC. The DPF may also be attached, nearer its other end, to a wall of an exhaust passage using support structures. To ensure that mating parts on the DPF and on the support structures align correctly during assembly, it is necessary to maintain tightly controlled machining tolerances on the mating parts. When an engine includes more than one DPF, stringent control on machining tolerances becomes even more necessary to ensure that DPFs can be assembled interchangeably in any of the multiple DPF locations. Alternatively, it is possible to match each DPF to a DOC and a corresponding support structure and assembly location to reduce the potential for mismatch between mating surfaces. Maintaining tight machining tolerances, however, increases the cost of manufacturing both the DPF and the support structures, and also increases the cost of any replacement parts.
One attempt to address the problems described above is disclosed in U.S. Patent Publication No. 2011/0167808 of Kosaka et al. that was published on Jul. 14, 2011 (“the '808 publication”). In particular, the '808 publication discloses a support structure for an exhaust gas treatment apparatus. The support structure of the '808 publication includes vertical support stays installed on the front and back sides of an engine body. In addition, the support structure of the '808 publication includes two support brackets. The ends of each support bracket are attached to the support stays using fasteners passing through elongated slots. The elongated slots in the support structure allow for bi-directional adjustment of the relative positions of each support bracket with respect to the support stays. An exhaust gas treatment apparatus is attached to the two support brackets using oversized holes for alignment with corresponding fastener holes on the support brackets.
Although the '808 publication discloses a support structure that provides some adjustability via the elongated slots and oversized holes, the adjustability may be limited. For example, the support structure of the '808 publication may permit only a limited amount of adjustment in a direction perpendicular to a plane formed by the brackets. Similarly, the support structure of the '808 publication may not be able to accommodate any angular mismatch between the exhaust gas treatment apparatus and the support brackets, about an axis perpendicular to the plane formed by the support brackets. Further, the support structure of the '808 publication may not allow for thermal expansion of the components. For example, an increase from an ambient temperature to an operating temperature may cause thermal expansion of the exhaust gas treatment apparatus, and the rigid support structure of the '808 publication may limit the amount of dimensional change. This could induce stresses, which may damage or even break components of the exhaust gas treatment apparatus.
The adjustable support structure of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.